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Step 1: Determining basic exposure time The aim is to determine the minimum UV exposure needed to obtain maximum black when printing through the transparency material on which the negative is printed. Coat a half-sheet of paper with the light sensitive emulsion of choice.
Place a sheet of transparency material on top to cover half of the paper. Place a sheet of opaque material so it covers both halves and leaves a strip exposed at the top. Make an exposure maybe one minute. Move the opaque material down to uncover another strip and make another exposure.
Continue this process until there is a series of increasing exposures extending across the junction between transparency material and no material. Develop the test sheet and dry it. Notice that on strips that received short exposures the boundary between transparency material and none can easily be seen.
The goal is to find the exposure where this boundary becomes invisible. This is the minimum exposure that is capable of giving maximum black through the transparency material or some other hue, e. Once the Basic Exposure is determined for that process on that paper it does not change.
If a final print turns out to be too light or dark, this is an indication of another problem in the workflow. Step 2: Negative contrast The second step in making a digital negative is to adjust the overall contrast of the negative to match the contrast range of the emulsion. For example, a palladium emulsion requires a negative with rather high contrast more ink.
A gum emulsion requires a negative with fairly low contrast less ink. The way this adjustment is done is by controlling the maximum amount of ink the printer lays down. Its default setting is 0 and we will leave it at that setting. The Default setting for the Color Density slider is 0 and this yields a relatively low contrast negative suitable for gum or cyanotype. Here is the workflow to determine the correct negative contrast to match the photo process.
Download the free Step Tablet image file at alternativephotography. Open the file in Photoshop. Flipping the image ensures that left and right handedness will remain correct when the ink side of the negative is placed against the emulsion side of the paper during print exposure. The following instructions are specifically for a Mac computer running Photoshop CS6 with an Epson printer. In the dialog box: Select the printer, Epson Stylus On the right side, under Color Management, check the button beside Document.
Presumably it will say Profile Gray Gamma 2. If it says anything else, go to the bottom, hit Cancel, bail out, go back and convert the image to gamma 2. If gamma 2. For Rendering Intent choose Perceptual the default. Select either Landscape horizontal or Portrait vertical media orientation. Click on Print Settings. Another window will open Figure C. Click on Layout and scroll down to Printer Settings.
Choose Paper Source usually the paper tray. Color toning, leave it at neutral. Output Resolution. Set at the maximum of dpi.
This is important for obtaining the highest quality negatives. With all these settings entered, go back up to the middle of the window and click on Advanced Color Settings. A window will open with an image of a blond woman off to one side and a bunch of various sliders Figure D.
Only change one thing in this window: Near the color circle is a box labeled Vertical. Type the number 75 into this box. This action causes the printer to throw the maximum amount of yellow ink into the image. Yellow is the strongest UV absorber after Photo Black.
Increasing yellow makes the UV more dense and negatives more contrasty. Hit SAVE. Move the Color Density slider to set the contrast of the negative Figure D2. Slide a sheet of transparency material into the paper tray, hit Print, and make a negative. Use a hair dryer to blow-dry the negative for a minute or two to get rid of all milkiness if the negative is to be used right away. Take the printed step tablet negative and use it to expose a sheet of paper coated with the photo emulsion, using the Basic Exposure Time determined in Step 1.
Process and dry the step tablet print. Now look at the area under the opaque plastic. This area has been coated by emulsion chemistry but has received no exposure. This reference area is the lightest tone obtainable with this particular emulsion. If the correct negative contrast setting has been chosen Color Density slider, remember? On the other hand, if several of the lightest steps look as white as the reference area, contrast is too high and it is necessary to move the slider to the left.
These varying contrasts will probably cover the entire range needed for most photo processes. When calibrating a new process, print a few and quickly determine which contrast setting will be necessary. When using Matte Black ink the Color Density slider is no longer needed. The entire range of contrasts needed for most photo processes can be obtained by changing the Max OD slider in the Advanced Black and White dialog from — 12 low contrast to 0 very high contrast.
Both Photo Black and Matte Black ink will produce good negatives. There is the option to use either one in case switching ink types is not desired. If making negatives for gum, casein, or cyanotype, use Photo Black ink and leave both sliders at their default positions. Step 3: Midtone adjustments To adjust image mid-tones a positive print of the step tablet shown in Figure A will be made, using a digital negative with its contrast adjusted for this particular photo process.
This print is then measured to find out how far off the mid-tones may be, and with this information a correction curve is constructed to bring the midtones back into perfect linearity. Once constructed, this correction curve will be applied to the positive image file. Print a digital negative of the step tablet. Flip the image horizontally, invert to negative, and print it on transparency material using the described printer driver settings, including the Color Density slider setting that gives the correct overall negative contrast for the photo process.
Expose this tablet negative to the photo emulsion using the Basic Exposure Time previously established. Process and dry the tablet print. Scan the tablet print using a flatbed scanner set to Reflectance Mode. Next, click on the Frame tab Figure F. Scan Type. Set the resolution slider to dpi low resolution is fine. Hit the Prescan button. The scanner will make a very low resolution scan of the entire glass.
Move the guidelines to limit the final scan to just the step tablet. Now go up and hit the histogram button at the top third button from the left. This will open up a histogram of the step tablet prescan Figure G. Move the shadow and highlight sliders so they are just outside of all the pixels the dark stuff. Make sure the middle slider remains at 0.
This will ensure that the scanner records all the information seen by the photo receptors and does not clip either the shadows or the highlights. Now go back to the main dialog box and hit Scan. The scanned image of the tablet print should open in Photoshop. Do the following things to this image: In Photoshop, go to the Windows menu, scroll down, and click on Info. The Info palette will open.
In the upper right corner click on a small stack of lines that open the Panel Options window. For the First Color Readout select Grayscale. Close Panel Options but leave the Info Palette open. Take a sheet of paper and write two column headings on it, Input and Output. Values in the Input column will be taken from the numbers written on individual steps of the step tablet.
Values in the Output column will be numbers read from the adjusted scan image of the step tablet print, measured with the Eyedropper tool. If the contrast selected via the Color Density slider for the step tablet negative is nearly correct the first number pair may read Input 0, Output 1. When done there will be two columns of paired numbers that will look something like Figure H. These number pairs describe a curve that shows how the image goes from pure white to pure black.
On the original step tablet file Input equaled Output which means the midtones are linear. On the scanned step tablet print Input will almost never be the same as Output since most photo emulsions respond to UV light in a nonlinear, S-shaped fashion.
Go to the top of the table, cross out Input and relabel it Output this operation is shown in Figure H.
Welcome to Precision Digital Negatives
Malalrajas Only change one thing in this window: In the upper right corner, click on the small lther of lines to open the Channel Options window. Lulu Staff has been notified of a possible violation of the terms of our Membership Agreement. Once constructed, this correction curve will be applied to the positive image file. Hold down the Option key while grabbing the dark slider with the mouse. An image palladiuj this step tablet is shown in Figure A. Place a sheet of opaque material so it covers both halves and leaves a strip exposed at the top. Following is a relatively simple three step method for making digital negatives.
How to Make Digital Negatives
DIGITAL NEGATIVES FOR PALLADIUM AND OTHER ALTERNATIVE PROCESSES PDF